1. Field of the Invention
The present invention relates to a sliding ball type constant velocity joint for a vehicle, and more particularly, to a sliding ball type constant velocity joint for a vehicle, which can minimize vehicle vibration by forming a track groove pair by two track grooves of an outer race and an inner race to reduce a contact area between the inner race and a cage, and can reduce the manufacturing cost by reducing the number of processing steps of the cage by forming the number of windows of the cage to half that of balls.
2. Description of the Related Art
In general, a joint functions to transmit rotational power (torque) between two rotation shafts which meet each other at an angle. In the case of a propeller shaft having a small power transmission angle, a hook joint, a flexible joint, etc. are used, and in the case of the driving shaft of a front wheel drive vehicle having a large power transmission angle, a constant velocity joint is used.
Since the constant velocity joint can reliably transmit power at a constant velocity even when an angle between a driving shaft and a driven shaft is large, the constant velocity joint is mainly used for the axle shaft of an independent suspension type front wheel drive vehicle. When viewed from a shaft, a tripod type constant velocity joint is provided to one end of the shaft which faces an engine (the inboard-side end), and a fixed ball type joint is provided to the other end of the shaft which faces a tire (the outboard-side end).
FIG. 1 is a cross-sectional view illustrating a conventional sliding constant velocity joint for a vehicle.
As shown in FIG. 1, the conventional sliding constant velocity joint for a vehicle comprises an outer race 2 which rotates by receiving rotational power of the engine (not shown) and is defined with grooves as track grooves 21 on the inner surface thereof, an inner race 3 installed in the outer race 2, a plurality of balls 4 for transmitting the rotational power of the outer race 2 to the inner race 3, and a cage 5 for supporting the balls 4.
The outer race 2 has a track groove 21 parallel with the center axis and a cylindrical inner diameter 22.
The inner race 3 has a track groove 31 parallel with a central axel and a spherical outer diameter 32.
In general, the plurality of balls 4 include six or eight balls.
The cage 5 has a spherical outer surface 51 having a spherical portion and a linear portion and a spherical inner surface 52 having a spherical portion.
Hereafter, the operation of the conventional sliding ball type constant velocity joint for a vehicle constructed as mentioned above will be described.
As the rotational power outputted from an engine (not shown) is transmitted to the outer race 2 through a transmission (not shown) and then transmitted to the inner race 3 through and the ball 4, so that then a wheel (not shown) is rotated.
The balls 4, which are restrained by a grinding surface 53 of the cage 5 and are also restrained between the track groove 21 of the outer race 2 and the track groove 31 of the inner race 3, transmits rotational torque. In this case, the spherical inner surface 52 of the cage 5 restrains the spherical outer surface 32 of the inner race 3, and the grinding surface 53 of the cage 5 restrains the balls 4, thereby enabling axial sliding and articulated joint movement. When the joint is articulated, the cage 5 and the balls 4 are positioned on a bisecting line of an operating angle, thereby enabling constant velocity movement.
Therefore, as the balls 4 slidably move in the track groove 21 of the outer race 2, the joint is articulated to follow the displacement of the vehicle.
However, the conventional sliding ball type constant velocity joint is configured such that axial power transmitted to the axially moving inner race 3 is transmitted to the spherical inner surface 52 of the cage 5 through the spherical outer surface 32 of the inner race 3 to push the balls 4. That is to say, the inner race 3, the cage 5, and the balls 4 are subunits, which move in the same axial direction at the same time, may not absorb idle vibration generated from the vehicle during idling but may transmit the same to a vehicle body.
In addition, in the conventional sliding ball type constant velocity joint, since the number of windows of the cage is equal to the number of balls, the number of processing steps for forming the cage may be increased, thereby undesirably increasing the manufacturing cost.